1. Field of the Invention
The present application relates to process of making a pemetrexed salt, in particular pemetrexed disodium.
2. Description of the Related Art
Pemetrexed and salts thereof are known as anti-folate, anti-neoplastic agents. Pemetrexed's chemical name is (S)-2-[4-[2-(4-amino-2-oxo-3,5,7-triazabicyclo[4.3.0]nona-3,8,10-then-9-yl)ethyl]benzoyl]amino-pentanedioic acid and has the following chemical structure:

The most common salt of pemetrexed is a disodium salt, i.e., pemetrexed disodium. Pemetrexed disodium has the chemical name L-Glutamic acid, N-[4-[2-(2-amino-4,7-dihydro-4-oxo-1H-pyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl]-, disodium salt. Pemetrexed disodium heptahydrate is the active ingredient of Eli Lilly and Company's ALIMTA® injectable composition. Pemetrexed disodium heptahydrate has the following chemical structure:

Various methods for preparing pemetrexed and pemetrexed disodium are disclosed in the art, such as International Patent Application Publication Nos. WO2001014379 and WO1999016742.
However, there is still a need for an improved process of making a pemetrexed salt.